The present invention relates to a method of fabricating a liquid crystal cell, and more particularly to a method of fabricating a liquid crystal cell wherein an alignment layer is patterned by irradiating an ultraviolet light into the selected part of an alignment material coated on a substrate so that a sealant may be properly printed on the substrate.
Liquid crystal molecules must be appropriately aligned to obtain a high contrast ratio and uniform brightness of a liquid crystal display. Alignment is achieved by rubbing two alignment layers which are coated on the opposing surface of two substrates, and in order to maintain the gap between the two substrates to a specified value, a spacer is deposited in a spraying operation in which static electricity assists the bonding of the to the substrate. After depositing the spacer, the substrates are sealed with a sealant and liquid crystal material is injected into the gap between the two substrates.
As the structure of liquid crystal molecules changes by an external applied voltage, the liquid crystal element obtained by the above described process can be used as a optical device. The optical characteristic of the LC element depends on the cell gap and the alignment uniformity.
FIGS. 1A-1F show a conventional process of forming an alignment layer on a substrate surface by roll coating. As shown in FIG. 1A, an alignment material is provided to the gravure roll 2 from the nozzle 1, and the alignment material is coated on the gravure roll 2 surface with a uniform thickness controlled by the doctor blade 3. Thereafter, as shown in FIG. 1B, the alignment material is rolled and moved onto the printing plate 5 which is formed on the surface of the printing roll 4. Then, as shown in FIG. 1C, the alignment material is rolled and coated onto the surface of a first substrate 6 which is laid on a moving plate 8. The thickness of the formed first alignment layer 7a as shown in FIG. 1D is controlled by the doctor blade 3, the concentration of the alignment layer forming material, and the pressure of the printing roll 4. Then, the first alignment layer 7a is baked and rubbed with a fabric in a chosen direction.
FIGS. 2A-2C show a conventional process of fabricating a liquid crystal cell. As shown in FIG. 2A, the first alignment layer 7a is applied on the first substrate 6 and a sealant A is printed on the first substrate 6. And, as shown FIG. 2B, a second alignment layer 7b is applied on a second substrate 9, and spacers B are deposited on the second substrate 9 to maintain a specified cell gap. Thereafter, as shown in FIG. 2C, the first and second substrates 6,9 are attached together. Then, the liquid crystal cell is obtained by injecting the liquid crystal into the gap between the two substrates 6,9.
In above mentioned method of forming an alignment layer, however, a part of the alignment material adhered onto the print plate is liable to be volatilized, and after coating the alignment layer on the substrate, a considerable amount of the alignment material remains attached to the print plate. Further, as shown in the FIG. 1E and FIG. 1F, the edges a,b of the alignment layer 7a coated on the first substrate 6 is deformed to cause an irregular alignment of liquid crystal molecules. Furthermore, the electrical interaction between the adjacent spacers causes disclination where the alignment of LC molecules is not defined.
In order to solve the above described problem of roll coating, the spin coating method can be performed, but because the alignment layer formed by the spin coating has a deformed outline, a sealant is liable to be formed on a part of the alignment layer, which can deteriorate the sealing property. Therefore, when a liquid crystal material is injected into the gap between the substrates, the liquid crystal material can leak out through the deteriorated sealing spot.